The present invention is related to power supply systems, and more specifically to wide range power supply devices. Such devices are used, for example, in protein electrophoresis, isoelectric focusing, DNA sequencing, and electrophoretic blotting.
Protein electrophoresis and isoelectric focusing demand power supplies that meet diverse requirements of delivering voltages from less than 20V to several kilovolts. Thus, these power supplies may be termed wide range power supplies. These power supplies also need to be efficient and able to perform in different modes such as the constant voltage, constant current, constant power, timed modes, and constant volt hour modes.
Current power supply configurations are impractical for achieving voltages as high as 5000V and do not provide high precision in the output voltage. For example, power supplies that use a flyback transformer require multiple windings whose outputs are rectified and connected in series to achieve high voltages. The many windings required for such high voltages create a bulky and expensive power supply. A flyback configuration, as well as other switching power supplies, also suffer from high electromagnetic interference (EMI) as follows.
For reasons of efficiency, size weight and cost, switch mode power conversion is a standard design. Switching power supplies generate EMI as a result of electric currents being switched at high frequencies. Regulatory requirements demand that this noise level be below certain prescribed guidelines to ensure that electronic equipment does not affect operation of other equipment in the vicinity. The magnitude of this EMI generated depends on the switching mechanism employed.
Hard-switched flyback converters have sharp rising and falling edges on the voltage waveforms and pulsating current waveforms, which generate relatively higher EMI. Thus, increased filtering is needed, which results in a higher cost of the end product. Also, the large number of windings on a flyback transformer causes poor coupling of magnetic flux between the primary and the secondary windings. This results in a higher leakage flux, which requires the additional cost of higher radiated EMI filtering. Running at high power, flyback transformers also generate relatively higher common mode EMI, which reduces efficiency of the power conversion stage.
The precision of current power supply configurations is also limited by the current switching and regulation mechanisms. For example, in a conventional architecture the power converter control is prone to time and temperature drift. Additionally, galvanic isolation of input and output is a design need so as to meet product safety and regulatory requirements, and current feedback patterns within using isolation circuitry produce offset errors and non-linearities.
Therefore, it is desirable to provide methods, apparatus, and systems for efficiently supplying wide voltage ranges with high precision and reliability.